The invention relates to a cylindrical hollow rod with an internal bore having a circular cross-section and ending in circular cavity openings at the two end faces of the hollow rod, composed of a shirred packaging tube, in particular of a shirred artificial sausage casing, in combination with a sheating which surrounds the hollow rod, leaving the cavity openings free, and an annular body at one of the two cavity openings. Hollow rods of this type, used as sausage casings, are also described as shirred casing sticks and their tubular outer wrapping as a support sheathing.
A combination of shirred tubular casing and support sheathing has been described, for example, in U.S. Pat. No. 4,263,942. In this arrangement, both cavity openings at the end faces of the hollow rod are deliberately left free, so that the filler horn can be introduced into the internal bore of the hollow rod without the outer sheathing having to be removed first. This arrangement has the disadvantage, however, that the outer support sheathing and the shirred casing stick arranged therein are not fixed to the filler horn during the filling step. When the packaging tube is drawn off the filler horn by the sausage meat forced in during the filling step and is thus unshirred, there is a risk of the unfixed support sheathing being drawn off in the same direction and thus passing into the brake which, as is known, is provided in the vicinity of the filler horn opening and is intended to press the unshirred packaging tube onto the filler horn and thus to delay the drawing off of the packaging tube.
This disadvantage is intended to be eliminated in EP-B-0,027,592 (FIG. 1) by means of a rubber ring, around which a net-like support sheathing is looped. During the filling step, the support sheathing is opened at the opposite end, whereby the tension of the rubber ring is loosened. The rubber ring then lays itself around the filler horn and is intended to hold the support sheathing firmly on the filler horn in this way. However, particularly firm fixing of the support sheathing is not achieved by the rubber ring so that, even in this embodiment, there is a risk of the net-like support sheathing being drawn into the casing brake.
The arrangement of U.S. Pat. No. 4,422,215 (FIG. 2) likewise allows fixing of a net-like support sheathing to the filler horn. According to this state of the art, one of the two cavity openings of the hollow rod is narrowed by the sheathing in a circular surface, so that the passage opening at this end face of the hollow rod has a radius which is smaller than the radius of the internal bore of the hollow rod. This narrowing of the cavity opening is effected by a flexible ring which is held in its position by a folded-back section of the sheathing. This ring comprises an annular, radially outward-extending flange part, which bears against the end face of the shirred casing stick and an annular sheathing section with several holding fingers which press the sheathing against the filler horn (FIG. 4 of U.S. Pat. No. 4,422,215).
It is also known, however, that the cross-section of the internal bore of shirred packaging tubes should always be as small as possible, because more space is then available for the folds of the packaging tube and a particularly large ratio of unshirred tube length to the length of the hollow rod is obtained. When the tubular casing is shirred, a shirring mandrel is therefore used, the diameter of which is as small as possible and approximately corresponds to the diameter of the filler horn, so that the shirred tube with its internal bore corresponding to the diameter of the shirring mandrel can still just be pushed onto the filler horn. If a ring, corresponding to U.S. Pat. No. 4,422,215 with an annular rubber section is then inserted into the end of the shirred casing stick, the shirred casing stick must either have a larger internal bore, so that the space required for the sheathing section of the ring is available, or there is a risk of the tube folds in this region being damaged by the sheathing section. Further disadvantages are that the sheathing section can be pushed over the filler horn surface only with difficulty when the shirred stick is applied to the filler horn and, on the other hand, does not provide a particularly firm hold, and in addition the manufacture of this ring, comprising a flange part and a sheathing section, is relatively expensive and requires a lot of material.